Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$23.89	6.718%	$25.4949	$25.49	$25.50	$25.50
Purchase #2	$235.63	5.201%	$247.8851	$247.89	$247.90	$247.90
Purchase #3	$132.91	11.794%	$148.5854	$148.59	$148.60	$148.60
Purchase #4	$144.48	5.523%	$152.4596	$152.46	$152.45	$152.50
Purchase #5	$216.83	3.149%	$223.658	$223.66	$223.65	$223.70
Purchase #6	$122.87	10.836%	$136.1842	$136.18	$136.20	$136.20
Purchase #7	$117.60	4.126%	$122.4522	$122.45	$122.45	$122.50
7 purchase totals =	$994.21		$1,056.7194	$1,056.72	$1,056.75	$1,056.90